SARAH is a research project that is funded by the French ANR (Agence Nationale de la Recherche) in the framework of the ARA SSIA (Action de Recherche Amont, Sécurité, Systèmes Embarqués & Intelligence Ambiante), from December 2005 to June 2009. The project involves four research laboratories: Valoria, LaBRI, XLIM and LITIS.


Delay-tolerant networking has recently emerged as an approach that might help achieve communication in challenged environments—such as mobile, wireless ad hoc networks—where end-to-end connectivity cannot always be obtained. In a delay-tolerant network, messages are not simply routed or disseminated in the network. While travelling from host to host, a message can be stored temporarily on certain hosts, and be forwarded later when circumstances permit. In a dynamic ad hoc network, where hosts can be present only sporadically in the network, this approach makes it possible for a message to eventually reach a target host, even if this host was not reachable at the time the message was sent originally. Moreover, delay-tolerant networking can allow message delivery in a partitioned network, using mobile hosts as carriers that can transport messages between non-connected fragments of the network.


Project SARAH relies on the assumption that delay-tolerant networking will be widely adopted in the near future as a means to support asynchronous communication in autonomous, partitioned ad hoc environments. Based on this hypothesis, we plan to consider the issues pertaining to the deployment and the utilization of distributed services on mobile devices capable of delay-tolerant, ad hoc wireless communication. Since no de facto standard for delay-tolerant networking has emerged yet, we plan to devise our own model for delay-tolerant ad hoc networking, and to implement a proof-of-concept middleware platform complying with this model. This platform will then serve as a framework for investigating the notion of delay-tolerant distributed services, that is, services that can be deployed in a partitioned ad hoc environment, and discovered and invoked based on a judicious combination of proximal and delay-tolerant communication. While devising these delay-tolerant communication middleware and services, special attention will be paid to the security issues introduced by the lack of end-to-end connectivity in the environment considered. Moreover, abstract modelling and simulation techniques will be used to evaluate and tune our communication model, and to observe how realistic delay-tolerant services can behave in a variety of networking conditions.